1. Field of the Invention
The present invention relates to a high performance fiber reinforced cementitious composition and a premix for producing the high performance fiber reinforced cementitious composition.
2. Description of the Related Art
Conventionally, single steel wires hooked at both ends are often mixed to cementitious composites (compositions) for the application to a tunnel spraying work or the like, but they are added only to prevent the peeling of concrete.
Further, fragments of fiber such as polyethylene are also mixed to the cementitious compositions to prevent a large cracking caused by tensile load.
The present invention has an object to provide a high performance fiber reinforced cementitious composition (composite) having high ductility (toughness) to both tensile load and compressive load when hardened.
The present invention further has an object to provide a high performance fiber reinforced cementitious composition having a good workability.
The present invention still further has an object to provide a premix (material) for producing the high performance fiber reinforced cementitious composition.
The high performance fiber reinforced cementitious composition (composite) (mixture) according to the present invention comprises fragments (pieces) of a steel cord stranded (twisted) wire accounting for 0.5 vol % or more and less than 1.5 vol %; and fragments (pieces) of at least one type of organic fibers accounting for 2.5 vol % or less.
The high performance fiber reinforced cementitious composition (mixture), in general, may further comprise cement, water and aggregates (sand, gravel, etc.) (the volume occupied by moisture is reduced in the hardened state) in addition to the above-mentioned steel cord stranded wire fragments (pieces) and the organic fiber fragments (pieces). Further, admixtures (a material other than water, cement and aggregate) including a water-reducing admixture (agent), etc. may be added to the high performance fiber reinforced cementitious composition.
The steel cord stranded wire fragment is composed of two or more mutually stranded single wires as described later, and spiral lines (of protruding shape or recessed-groove shape) are present on the surface of the steel cord stranded wire fragment overall since the respective single wires are spirally deformed. Accordingly, the surface of the steel cord stranded wire fragment has high frictional resistance over the whole length. The high performance fiber reinforced cementitious composition in itself is resistant to a large compressive load when hardened, because it is a cementitious material. Further, since the fragments of the steel cord stranded wire randomly present in the hardened high performance fiber reinforced cementitious composition resist the stress acting in a direction orthogonal to the application direction of the compressive load, the ductility (toughness) in the orthogonal direction of the hardened cementitious composition is enhanced. Moreover, the fragments of the steel cord stranded wire randomly present in the hardened high performance fiber reinforced cementitious composition also act to enhance the ductility to tensile load. The hardened high performance fiber reinforced cementitious composition is consequently provided with high ductility to both compressive load and tensile load.
The steel cord stranded wire fragment may be composed of three or more stranded steel-made single wires, and the way (method) of stranding (twist) may be optionally determined. When the stranding pitch magnification [the stranding pitch length (mm)/the diameter (mm) of steel cord stranded wire fragment] is 15 or less, the steel cord stranded wire fragment is difficult to fray, and the adhesion to cement is also sufficiently ensured. The cut surface of the steel cord stranded wires may be subjected to welding or the like to prevent the fraying.
The length of the steel cord stranded wire fragment is 15 mm or more and 45 mm or less. When the length of the steel cord stranded wire fragment is 15 mm or more, the high ductility to compressive load and tensile load can be kept as described above. When the length of the steel cord stranded wire fragment is 45 mm or less, the mutual tangles of the steel cord stranded wire fragments can be prevented when kneading the steel cord stranded wire fragments with cement, water, aggregates and the like for the production of the high performance fiber reinforced cementitious composition, and the fluidity can be thus ensured to enhance the workability.
The steel cord stranded wire fragments can be efficiently produced by cutting a steel cord stranded wire in the above-mentioned length.
In the high performance fiber reinforced cementitious composition according to the present invention, the fragments of the steel cord stranded wire accounts for 0.5 vol % or more and less than 1.5 vol %. With 0.5 vol % or more, a brittle failure (fracture) by the cracking caused by tensile and compressive loads can be prevented. With less than 1.5 vol %, the mutual tangles of the steel cord stranded wire fragments can be prevented when kneading the steel cord stranded wire fragments with cement, water, aggregates and the like for the production of the high performance fiber reinforced cementitious composition, and the fluidity can be thus ensured to enhance the workability.
The concept of the organic fiber includes chemical synthetic fiber such as polyethylene, vinylon and aramid, and the organic fiber may be a single filament, fiber, thread or string, or a twisted or stranded one. The fragments of the multiple organic fibers mixed to the high performance fiber reinforced cementitious composition can prevent the large cracking caused by compressive load or tensile load. Accordingly, the high performance fiber reinforced cementitious composition material with the organic fiber fragments mixed thereto is improved in compressive strength and tensile strength, and high ductility to compressive load and tensile load can be provided.
The diameter of the organic fiber fragment is smaller than that of the steel cord stranded wire. Therefore, since the organic fiber fragments are bonded to cement in a range (radial direction) smaller than the steel cord stranded wire fragments are, the high performance fiber reinforced cementitious composition comprising the both can be provided with ductility further higher than the ductility obtained in a one comprising only the steel cord stranded wire fragments.
Organic fiber fragments having various diameters can be used. When the usable organic fiber fragments are defined on the basis of aspect ratio, the aspect ratio of the organic fiber fragments is 2500 or less. According to this, the high ductility to tensile load and compressive load can be kept, and the mutual tangles of the organic fiber fragments can be prevented when kneading the steel cord stranded wire fragments and the organic fiber fragments with cement, water, aggregates and the like for the production of the high performance fiber reinforced cementitious composition.
When the multiple organic fiber fragments account for 2.5 vol % or less, the high ductility to tensile load and compressive load can be kept. Further, in the production of the high performance fiber reinforced cementitious composition, the organic fiber fragments provide proper viscosity in the kneading to prevent the settlement of the steel cord stranded wire fragments. Consequently, since the steel cord stranded wire fragments are properly dispersed, and the multiple organic fiber fragments are also dispersed without tangling, the fluidity can be ensured to enhance the workability. The organic fiber fragments further preferably account for 1.5 vol % or less. Although the use of the organic fiber fragments is dispensable, the mixing thereof would be better off, or 0 vol % is not included (except or more than 0 vol %, hereinafter the same as above). More preferably, the organic fiber fragments of 0.1 vol % or more can provide the effect of ductility.
The high performance fiber reinforced cementitious composition of the present invention is used as civil engineering and building materials such as column material and wall panel. The hardened high performance fiber reinforced cementitious composite material may be a part of a structure. (e.g., column, etc.)
In the production of the high performance fiber reinforced cementitious composition, the steel cord stranded wire fragments of 0.5 vol % or more and less than 1.5 vol %; the organic fiber fragments of 2.5 vol % or less (preferably not including 0 vol % although 0 vol % may be adapted, more preferably 0.1 vol % or more, which can provide the effect of ductility); cement of 20 vol %-35 vol %; water of 35 vol %-55 vol %; and aggregates of 25 vol %-35 vol % are mixed. These are kneaded to disperse the steel cord stranded wire fragments and the organic fiber fragments, and then poured to a form of an optional shape followed by hardening.
A premix (material) (except water and aggregates) for producing the high performance fiber reinforced cementitious composition of the present invention comprises fragments of a steel cord stranded wire accounting for 1.3 vol % or more and less than 6.9 vol %; fragments of at least one type of organic fibers accounting for 10.8 vol % or less (preferably not including 0 vol % although 0 vol % may be adapted, more preferably 0.4 vol % or more, which can provide the effect of ductility); and cement accounting for 83 vol % or more and less than 98 vol %.
Another premix (material) (except water) for producing the high performance fiber reinforced cementitious composition of the present invention comprises fragments of a steel cord stranded wire accounting for 0.68 vol % or more and less than 3.6 vol %; fragments of at least one type of multiple organic fibers accounting for 5.8 vol % or less (preferably not including 0 vol % although 0 vol % may be adapted, more preferably 0.2 vol % or more, which can provide the effect of ductility); cement accounting for 34 vol % or more and less than 63 vol %; and aggregates accounting for 34 vol % or more and less than 63 vol %.
When such a premix (material) for producing the high performance fiber reinforced cementitious composition is used, the premix (material) can be mixed and kneaded with a required prescribed quantity of water and the like without paying attention to the mixing quantity of the steel cord stranded wire fragments, the organic fiber fragments or the like when the high performance fiber reinforced cementitious composition is produced in a construction site. Accordingly, the efficiency of the work can be enhanced. The premix (material) can be laid in a portable state by putting it in a bag, a container or the like.